Don't use 6.5, it's more than 5 years old and riddled with security bugs. Run a yum update to get the rest of your server up to date. There are many much more important and exploitable vulnerabilities in 6.5 than just meltdown/spectre.

CentOS 5 died in March 2017 - migrate NOW!
Full time Geek, part time moderator. Use the FAQ Luke

Yes, we have CentOS upgrade in pipeline and it involves huge effort in porting our product/deployment. We will be working on it.

Just to understand the recent changes in the kernel patches, earlier version of kernel & dracut patches (kernel-2.6.32-696.18.7.el6.x86_64,
kernel-firmware-2.6.32-696.18.7.el6.noarch, dracut-kernel-004-409.el6_8.2.noarch, dracut-004-409.el6_8.2.noarch) haven't fixed the Spectre Variant 2 but the recent one fixed it (without any BIOS / Intel patch).

That depends on what processor you have. The RHEL microcode_ctl package ships updated microcode but they can only ship what Intel has made available and they haven't fixed every processor that was ever released. If you yum update then you will get the latest kernel and the latest microcode_ctl package too. Once you reboot into those you should have as much fixed as it's currently possible to fix.

CentOS 5 died in March 2017 - migrate NOW!
Full time Geek, part time moderator. Use the FAQ Luke